JPS60190505A - Slag cutting method during tapping of molten steel - Google Patents

Abstract

PURPOSE:To improve remarkably a slag cut rate and to eliminate the adverse influence of slag even if the slag flows out by blowing off cooling powder from the top end of a stopper and making an operation to shut the stopper in the stage of discharging a molten steel from the tap hole of a vessel. CONSTITUTION:A stopper body 8 is held right above a tap hole 2 and existing slag 4 at the same instant when tapping from a converter 1 is started. While the powder from a powder supply device 12 is discharged through a discharge hole 7, the body 8 is immersed into the molten steel until the hole 7 is made flush with the boundary plane between the slag 4 and a molten steel 3 to solidify and reform the slag 4 around the body 8. The melt surface of the steel 3 falls upon lapse of the tapping time but the stopper body is lowered to follow up said surface by a stopper arm 10. The molten steel 3 is discharged at the end period of tapping and the solidified and reformed slag 5 approaches to the hole 2 then the hole 2 is closed by a stopper head 6 at the same instant when the slag 5 is discharged through the hole 2. A gap is generated between the head 6 and the hole 2 in this stage but is closed by the slag 5.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a method for cutting slag at a pouring hole of a container storing molten metal, such as a converter tap hole, a ladle pouring hole, a pouring hole of a tundish for continuous casting, etc. It is about law.

(Prior art) As a prior art, there is a method for preventing slag discharge during tapping in a converter disclosed in Japanese Patent Application Laid-open No. 54-28219, which involves spraying high-pressure N2 gas onto the bath surface at the top of the tapping hole during tapping. Remove slag and add flux such as 0a-0 to it (P2O5)
This is a method of forming a slag layer with a low concentration.

However, this method uses gas to remove the existing slag without immersing the nozzle, so a large amount of gas is required for spraying, and a large amount of fresh CaO is also required.

In addition, the surface of the slag that comes in contact with the atmosphere immediately cools and solidifies.
Removal by gas blowing has drawbacks such as being extremely difficult in actual practice.

Furthermore, in the slag separation method disclosed in Japanese Patent Application Laid-open No. 58-123814, the tip of the slag stopper is shaped like a brim with a large diameter. However, this method cannot follow changes in the shape of the tapping hole, making perfect slag cutting impossible, and increasing the cost of refractories. Further equity 39-5322
The method of adding additives to molten steel in the publication is that when molten steel is injected into a mold, the tip of the stopper is made hollow, and additives such as AA are added to the injection stream along with a carrier gas through the hollow rond, and the components of the molten steel are This is for adjustment and not for solidifying the slag. Furthermore, there is no disclosure regarding the slag cutting method.

(Object 1 of the invention) This invention dramatically improves the slag cutting rate compared to the slag cutting method of the prior art, and also prevents the slag from having an adverse effect even if it flows out. This paper presents a new slag cutting method.

(Structure, operation, and embodiments of the invention) The present invention solves the drawbacks described in 1- below, and its gist is that when molten steel flows out from the container spout, the interface between the molten steel and floating slag is removed from the tip of the stopper. Cooling powder is blown into the vicinity to solidify and reform the floating slag, and
This is a slag cutting method when pouring molten steel, which is characterized by performing a stopper closing operation.

Next, an example of the present invention will be described in detail with reference to FIG.

Figure 1 shows the usage situation in a converter, where 1 is a converter, 2 is a converter, and 2 is a converter.
3 is the steel tapping hole, 3 is the molten steel, 4 is the pre-nullage, 5 is the solidified or modified q
Q-shaped slag, 6 is a stopper head, 7 is a powder discharge hole, 8 is a stopper main body, 9 is a powder supply pipe, 10 is a stopper arm, 11 is a stopper drive device, 12 is a powder supply device, 13 is a It is a gas body.

In the present invention, powder is blown from a powder supply device 12 through a powder supply pipe 9 through a powder discharge hole 7 onto the interface between existing slag 4 and molten steel 3 to form solidified or modified slag 5. . This operation of causing the powder discharge hole 7 to follow the boundary surface between the slag 4 and the molten steel 5 is performed by operating the stopper main body 8 via the stopper arm 10 using the stopper driving device 11 .

The interface between the slag 4 and the molten steel 3 can be detected by the vibration of the stopper arm 10 or the stopper main body 8 at the corner of the converter during powder injection. That is, the vibrations generated during the injection in the existing slag 4 are small, and the vibrations in the molten steel 3 are large.

Next, we will describe the slag cutting method in its nature.

At the same time as the converter 1 starts tapping, the stopper main body 8 is held directly above the tapping hole 2 and the slag 4, and while discharging powder, the powder is deposited on the interface between the slag 4 and the molten steel 3. The slag 4 surrounding the stopper body 8 is assimilated and modified by immersion so that the discharge holes 7 are aligned with each other.

At this time, the level of the molten steel 3 decreases with the elapse of time after tapping, but the stopper arm 10 follows it. Subsequently, at the end of the steel tapping stage, 33 molten steel was discharged at JJl.
The solidified and modified slag 5 approaches the tapping hole 2, and at the same time as the solidified and modified slag 5 moves from the tapping hole 2 to 1ll-1'43, the stopper head 6 closes the tapping hole 2.

At this time, a gap is generated between the stopper head 6 and the tapping hole 2, or the gap is closed by the solidified and reformed slag 5. After the slag cutting is completed, the stopper arm 10 is activated at the same time as the tilting of the rotary pj1 is returned to stop the powder injection and the powder is taken out of the furnace.

In the present invention, the area near the interface refers to, for example, 70'm on the slag side and 70'm on the molten steel side, centered on the interface between floating slag and molten steel.
This range covers a range of about 100 m and can be selected as appropriate depending on the properties of the slag.

Next, examples of the present invention will be given.

Molten steel (composition (%)) after blowing in a 250t oxygen top-blowing converter
, a: 0.03, Mn: 0.23, p: 0
．． 02, S: 0.01, Fe: balance, temperature 1660°C), floating slag (component (%1 oao:
52.5i02: 19, MnO: 5, P2O5: 3
, S: 4, MgO: 1, T, Fe: 10, thickness 300 mm) and the molten steel.
a0500KLi/min, size 1.5mmφ average), gas (Ar40ONrr?/Hr) was blown for 3 minutes to solidify and modify the slag layer (range 1000mmφ)
while generating a stopper head (diameter 500mmφ)
When the tapping hole (diameter 250 mmφ) was closed, 0.4 t of slag was discharged into the ladle.

I measured the phosphorus content of this slag, but it was very small.
The treated slag had been subjected to the modification rL1, and of course no rephosphorization was observed.

(Effects of the Invention) As described above, the present invention completely cuts the slag by filling the gap between the stopper head and the tap hole, which has been considered a drawback in the past, with solidified and modified slag.
There was also very little slag mixed into the pot.

The slag cutting rate of the present invention is 98%, and the IC
In contrast, the spray method (Japanese Patent Application Laid-Open No. 54-28219) cut 185% and the one-stopper type (Shokai Sho, 58-123).
No. 81'4) had a cut rate of 1%.

Furthermore, the carrier gas for powder supply is also conventional technology (Unexamined Japanese Patent Publication No. 54
．． , -28219 Publication), it is possible at 400 Nrn71Ar, which is about 1/20, compared to 80001 W/Hr.

As described above in detail, the present invention is effective in cutting slag, requires less powder and gas, and contains 10,000 to 111 slags in the poured molten steel. Since the slag is rendered harmless even if it escapes, this slag cutting method is extremely effective in that there is almost no deterioration in the quality of the steel due to rephosphorization or the like.

[Brief explanation of the drawing]

FIG. 1 is a detailed explanatory diagram of the present invention. 2 = Tap hole 5: Modified slag layer 6: Stopper head 7: Powder discharge hole 12: Powder supply device

Claims (1)

[Claims] When molten steel flows out of the container spout, cooling powder is blown out from the tip of the stopper near the interface between the molten steel and floating slag, solidifying the floating slag, modifying Tj, and closing the stopper. Slag cutting method when pouring molten steel.